Thursday, 20 February 2020

EA says ‘we are in uncharted territory’ – so why doesn't the MWWT reflect that?

New Met Office figures show that February could be Devon's wettest on record:
At the current rate, Devon is averaging 8.44mm of rain a day. If that continues throughout the month, that will bring the 2020 total to 244.8mm - a new record.
What bearing will this have on groundwater levels at Straitgate? Who knows? Certainly not the Environment Agency, Devon County Council or Joe Public. Aggregate Industries, "in-line with company policy", has put a stop to timely scrutiny of these figures. That's something that should make people nervous. What could it be wanting to hide?

According to DevonLive:
The last major washout in February came in 2014, when a massive 226.8mm fell.
The wettest February in Devon on record was 243.7mm in 1990.
Both of those years have a significance for Straitgate.

2014 was the year in which the groundwater levels recorded at Straitgate were used by Aggregate Industries to predict the maximum winter water table at the site – the MWWT, the base of any quarry.

1990 was the year in which groundwater was recorded 2.8m higher than this prediction, a level the EA argued was "difficult to judge its significance", but now concedes should be taken into account.

The EA’s endorsement of Aggregate Industries’ MWWT model is based on the Agency’s belief that groundwater levels recorded in 2014 – shortly after monitoring first started – were the highest ever, despite levels in some places being significantly higher in 1990 and 2018. Based on this belief, the EA is willing to write off the normally required unquarried buffer to protect drinking water supplies. This means there’s no margin for error, no margin for MWWT modelling inaccuracy, no margin for contamination, no margin for digger driver cock-up.

It turns out there is no margin for the past either. The EA is correct that 2014 was a wet year in the South West. However, according to the Met Office, 2012, 2000, 1994, 1960, 1924, 1903, 1882, 1877 were all wetter. Might the MWWT have been higher in any of those years? No allowance has been made for this.

Furthermore, there is no allowance in the MWWT for what climate change might bring. BGS says:
Climate change will increase temperatures and change rainfall across England, Scotland and Wales. In turn, this will modify patterns of river flow and groundwater recharge, affecting the availability of water and changing the aquatic environment.
What's going to happen to the winter water table at Straitgate, given that the Met Office forecast:
Of course, such increases in winter rainfall will – as we are already witnessing – have a devastating impact on many places. At least one person at the Environment Agency gets it:




Given that we are in "uncharted territory", given that winter rainfall could increase by up to 35%, given that groundwater recharge will be affected – why does none of this inform Aggregate Industries’ MWWT guesstimate? Why is there no allowance for the future?

Where will the maximum winter water table – the actual one, not the suggested one – be at Straitgate Farm in 50 years time, 100 years time? If Aggregate Industries did quarry to its idea of the MWWT – could the farm be left under water for months on end in the not too distant future?
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